WHO doesn’t root for an Albert Brooks movie? His smart, urbane, casually genteel style of comedy is so out of sync with today’s fashionably vulgar comic filmmaking as to be positively countercultural. Go, Albert Brooks!

Alas, for those of us starved for evidence that tastefulness and humor are still on speaking terms at the movie house, “The Muse” is a major letdown. It’s good for some sterling one-liners and a generous handful of sparkling scenes, but after a strong, peppery start, the movie collapses into bland mush for want of anything interesting to say.

Middle-aged Brooks must be feeling acutely his alienation from the Hollywood mainstream, in which Adam Sandler rakes in kabillions for his pee-pee jokes and a movie featuring sex with a pastry proves a hit with young audiences.

In “The Muse,” his usual incarnation of his amusingly neurotic self is called Steven Phillips, and he’s a veteran screenwriter in desperate need of a hit. Steven has reached the point in his career where he’s receiving awards for his good works, as distinct from his good work. Leaving a ceremony at which her dad was feted, Steven’s little girl asks, “Daddy, what’s a humanitarian?”

“Somebody who hasn’t won the Oscar,” he answers. Steven suffers through a humiliating meeting with a callow young Paramount executive (Mark Feuerstein), who tells Steven he’s lost his edge and terminates the studio’s deal with him.

Desperate, sad-sack Steven visits his hot, Oscar-winning screenwriter friend Jack (Jeff Bridges, of whom we see too little here), seeking the secret of his success. Jack’s muse really is a Muse, and she lives in the guest house nearby. The Muse is played by Sharon Stone, who spins the minor goddess as a delicious caricature of a petulant film diva.

The flighty Muse agrees to help Steven write a hit, as she’s helped so many of Tinseltown’s players (there is a string of very funny cameos by the likes of Rob Reiner, Martin Scorsese and James Cameron, all kvelling over the Muse’s powers) – but only if he’ll cater to her every whim. This proves costly, given her exotic tastes (baubles from Tiffany’s, a suite at the Four Seasons, and so forth). Eventually, she demands to move in with Steven’s family, much to the suspicious chagrin of his wife, Laura (Andie MacDowell).

But the Muse then turns her helpful affections (she’s like the Martha Stewart of career redecorating) to Laura, whom she encourages to start her own business – leaving needy and jealous Steven fuming over whether he’ll ever be rid of this capricious creature.

“The Muse” is a satire of Hollywood’s congenital obnoxiousness and epidemic insecurity. Brooks skewers a movie biz that desperately chases after “edgy,” whatever that is, and which fosters creative types so insecure they’re willing to believe in anyone, even a New Age mystic who promises to guarantee them a hit.

That’s not exactly news, but for the first half of “The Muse,” Brooks mines jeweled jibes and insider-y laughs from the shopworn premise. I don’t know why Brooks’ own muse seems to have hit the road at the halfway point here, but as soon as Sharon Stone moves in with the family, the delicate “Muse” deflates like a souffle.

The beautiful Andie MacDowell’s usual dullness sucks the life out of every scene, even with Stone showing real comic flair (who knew?!), doing her energetic best to pump life into this wheezer.

The real problem, though, is that Brooks and co-screenwriter Monica Johnson run out of inspiration long before the finish, leaving “The Muse,” which begins so briskly and promisingly, to stumble aimlessly and flat-footedly toward a surprise finale.